Semiconductor apparatus



July 21, 1959 R. J. ZELINKA SEMICONDUCTOR APPARATUS Filed March 21, 1958 VOLTS CURRENT- MILLIAMPERES INVENTOR.

RICHAQD J. ZELINKA ATTORNEY QWMJRM United States Patent 6 8 Claims. (Cl. 323-22) This invention relates generally to improvements in a semiconductor related power supply apparatus for controlling the voltage to a load device, and is more particularly related to a semiconductor voltage regulator circuit for controllingthe power form an electrical source to. a load, or to variable. loads whereby thesemiconductor voltage regulated power supply must operate over wide extremes of current variation, for example, from a few milliamperes. to relatively large currents in the order-of five amperes or greater. ther related to a particular type of semiconductor regulator' circuit for maintaining a relatively constant outputtoa load over wide variations of'load impedance, which This invention is fur- Cfi diode is connected adjacent the load to be'regulated, the resistive leg of the bridge is placed upstream and a compensating resistor is placed in series with the supply conductor between the reference and the sensing leg of the bridge type circuit, and which circuit is selfprotecting in the event of abnormal overload.

regulator is 'arrangedto beself-protecting against shorts or near shorts in. the output terminals or load device.

It has been proposed in. the prior art to provide a transistor voltage regulator having a plurality of direct coupled triode transistors, the initial stage which-has its input electrodes connected to sense the output voltage ofthe regulator and which has its final stage connected in series with one of' the power supply leads. The output impedance of the final transistor stage is controlled as a function of the output potential to the loadtoprovidea regulated potential thereto. In the practical application of the transistor voltage regulators disclosed in the prior art, it has been discovered that if the load device or theoutput terminals of the voltage regulator become shorted, the transistor voltage. regulator is destroyed,

generallybecause of excess power dissipation in the series regulating triode transistor. An'explanation-of this failure is that inasmuch as three or more transistors areamplified by the succeeding transistors so that the finali regulating transistor cannot actually be shut oil. In one fairly complex circuit this fault is minimized by the provision ofan auxiliary reverse bias to the baseof the i final triode transistor stage.

Applicant has discovered that by utilizing a tetrode transistor as the final regulating stage, and by shorting one base electrode of the tetrode transistor to the emitter electrode, the circuit can be made to be fail-safe even though the output terminals of the regulator are-directly shorted together. A rearrangement of the apparatus for sensing the outputvoltage to the load is also significant in the improved operation of the voltage regulator of this invention.

It is an object of this invention to provide animproved semiconductor voltage regulator power supply which can provide a relatively constant output volta'geyover wide extremes of load current and which is self-protecting against abnormally high load currents.

Another more specific object of this inventioniis to provide a semiconductor voltage regulator for controlling the voltage from a supply source to a load,-which regu-'- lator has an improved bridge type-voltage sensing circuit 1 in which the bridge leg containing the Zener reference These and other objects of the invention will become more apparent upon a consideration of the specification, claims and drawing of which:

Figure l is a schematicrepresentation of an embodimentof the invention;

Figure 2 isa graphical representation of the voltage current characteristics of the Zener reference diode; and

Figures 3 and 4 show diagrammatically the construction ofa preferred type of tetrode semiconductor device for use in this invention, Figure 3 being a top plan view ofthe device and Figure 4 being a vertical sectional view taken along the lines and in the direction of the arrows 44 of Figure 3.

Referring now to the circuit of Figure 1 there is disclosed a source of electrical power having positive and negative output terminals 11 and 12, respectively. The-positive terminal 11- is'connecte d through a com ductor 15 to the emitter of a power tetrode semicon ductor-device 21 here shown in the form of a junction tetrode transistor. -The tetrode transistor also includes a collectorgelectrode 22, a first base electrode b and a entitled Semiconductor Device, Serial No. 556,210,

filed December 29, 1955 ,-and assigned to the same assignee' as the presentinvention.

The collector electrode 22 oftetrode transistor 21 is connected -by a conductor 23, a compensating resistor 24 anda conductor 25 to positive output terminal'26 of the voltageregulator. The base electrode b is directly connected by a conductor 17 to a junction 16 on the conductor 15, thereby directly shorting the base electrode b tothe emitter 20. The base electrode b, of tetrode transistor 21is connected by a conductor to an emit-- ter electrode-31 ofa semiconductor amplifying device 32, here shown as a junction triode transistor of the p-n-p type. --The semiconductor device 32 also includes a base electrode 33 and a collector elect-rode 34. The collector electrode 34 is connected bya conductor 35 to a junction 36-on the conductor 23. The base electrode 33 of transistor- 32 is connected by a conductor 37, a current limiting resistor 40 and a conductor 41 to the collector electrode 42-01 a semiconductor amplifying device 43, here shown as an n-p-n junction type transistor. The device 43'also includes a base electrode 44 and an emitter electrode 45. I

The output voltage of the regulator is sensed by a bridge. type arrangement which include two impedance circuits-connected acrossthe output voltage terminals.

In-this circuit the reference leg is connected downstream 1 of the compensating resistor 24 and can be traced from a junction 46 on the conductor 25 through a conductor 47, a Zener diode 50, a conductor 51, a junction 52, a conductor 53, and through a resistor '54, to a junction on the negative conductor 13; The sensing leg of the bridge is located upstream of the compensating resister- 24 and the circuit maybe traced from a junction on the conductor 23 through a resistor 61, a potentiometer-62 and a resistor 63 to a junction 64 on the negative conductor 13. The potentiometer 62 includes animpedance element 65 and an adjustable'wiper 66 inmovable contact with the impedance element 65. The controlling potential from this bridge type arrangement is obtained between' the potentiometer wiper and the junction 52 located between the Zener-diode 50 and the transistor 54. A conductor 67 directly interconnects the wiper 66 to the base electrode 44 of the transistor 43. A conductor 68 directly interconnects the emitter electrode 45 of transistor 43 with the junction 52, the controlling potential from the bridge type circuit is connected to the input of transistor 43.

Figures 3 and 4 disclose an embodiment of the tetrode transistor device of the co-pending application, mentioned above. The transistor of Figures 3 and 4 includes a semiconductor body or wafer 70 which has a pair of rectifying junction electrodes 71 and 72 sltuated in concentrically disposed relationship on a pair of parallelly disposed surfaces 73 and 74, respectively. The

rectifying junction electrode 71 is the emitter electrode and is situated between a pair of ohmic contact baseelectrodes 75 and 76. The emitter electrode is preferably of somewhat smaller width dimension than is the corresponding collector electrode 72. An ohmic path exists across the base wafer from base electrode 12 to b with the majority of the resistance being in the bridge area between the emitter and collector junctions. The details of this device are more clearly set forth in the copending application, above referenced. It will be appreciated that the tetrode transistor 21 of Figure 1 may well represent a partial view, i.e. the right or left half of the transistor as shown in Figures 3 and 4.

In considering the operation of this voltage regulator circuit, let us assume initial operating conditions such that potentiometer wiper 66 has been adjusted to maintain the desired potential across the output terminals 26 and 14 to the load device R In one successful embodiment of this invention, a 24-32 volt power source was regulated to provide a 22 volt output to the load with load currents varying from milliamperes to 3 amperes.

As can be seen from the drawing in Figure 1, the resistors 61, 62 and 63 together with the Zener diode 50 and the resistor 54 provide a bridge type potential sensing means. A current path may be traced from the positive conductor 25 through the Zenar diode 50 and through the resistor 54 to the negative conductor 13. It will be noted that the emitter current from transistor 43 also flows through the resistor 54 to the negative conductor 13. In Figure 2 there is shown a plot of the characteristic curve of volts versus current of a typical Zener diode. In the normal use of a Zener diode as a reference potential it is the manufacturers recommendation that the Zener diode be operated from a minimum of (point a, Figure 2) 10 milliamperes current and up, so that the diode will be operating in the linear portion of the voltage curve. In applicants invention the rethe potentiometer wiper 66 through the transistor 43 from base electrode 44 to emitter 45 and through the conductor 68 to the junction"52. The transistor 43 is thus rendered conductive to a predetermined amount, and the output current flowing in transistor 43 from the collector electrode 42 to the emitter 45 may be traced through a path commencing at the positive power source terminal 11 and flowing through the conductor 15, from emitter 20 to base electrode b of tetrode transistor 21,

through-the conductor 30, from emitter 31 to base electrode 33 of transistor 32, through conductor 37, current limiting resistor 40, conductor 41, through transistor 43 from collector 42 to emitter electrode 45, through conductor 68 to junction 52, and through the resistor 54 to the negative conductor 13 and thus back to the power source. The base current flowing in transistor 32 also renders the transistor 32 conductive and current also flows from the emitter 31 to collector electrode 34 and through the conductor 35 to conductor 23. The

emitter current flowing into transistor 32 must flow out of the base electrode 11 of tetrode transistor 21 and thus the conductivity of the tetrode 21 is controlled by the conduction of transistor 32. Thus it can be seen that the voltage diflerence between the potentiometer to increase, causing the conductivity of transistors 43,-

32 and 21 to be increased. This increase in conductivity of regulating transistor 21 tends to increase the voltage supplied to the output terminals 26 and 14.

The compensating resistor 24 which is connected in series between the conductors 23 and 25 counteracts the droop of the system so that the output voltage is maintained at the rated value over the design current limits of the regulated power supply. The compensating resistor is preferably a very small value, for example, it may be' in the order of a fraction of an ohm. It will be noted that the voltage drop across the compensating resistor due to increasing load current is in a direction sistor 54 is chosen large by design to limit the maximum current flowing in the Zener diode to approximately 2.5 milliamperes (Figure 2, point b) at rated output voltage of the regulator, when no emitter current is flowing in the transistor 43. In this invention therefore the Zener diode is biased above but near the knee of the diode Zener curve.

to increase the potential drop between junction 60 and junction 52 and thus to increase the potential difference between potentiometer wiper 66 and the junction 52. By proper choice of the value of compensating resistor 24,

the regulator can be designed to have a flat, a falling,

' or a rising characteristic.

It will be noted that transistors 43, 32 and 21 are di- 7 rectly coupled in a cascade arrangement so that the output current of one transistor is the control current of the following stage. The emitter 45 of transistor 43 is connected to a junction 52 and the base electrode 44 is connected to the potentiometer wiper 66. Thus the input electrodes of transistor 43 are connected to the output terminals of the bridge type voltage sensing means.

As we have initially assumed, the regulator is operating such that the conductivity of transistor 21 is being maintained in a condition to maintain the output voltage constant. To maintain this condition, the potentiometer wiper 66 has been adjusted to make the potential on the wiper 66 slightly positive with respect to the reference potential at the junction 52 between the Zener diode and the resistor 54. The result of this potential difference is to cause a current to flow from reduction in the load impedance.

An important feature of the operation of applicants invention is that the voltage regulator circuit cannot be damaged by overload conditions such as may occur by shorting of the output terminals or by an abnormal Let us assume, for purposes of explanation, that the circuit is designed to provide voltage regulation for load currents from 10 milliamperes'up to 3 amperes, and that upon the regulated power' supply being required to provide current substantially in excess of 3 amperes due to an overload condition, the voltage regulator circuit will drive tetrode transistor 21 to a non-conductive state and thereby remove the power source from the load until the overload condition is remedied, at which time the voltage regulaincreases, results in an increasing emitter current flowing out of'emi-tter 45 and through the resistor 54. This increase in emitter current flowing through the resistor 54 causes a decrease in the current flowing through the Zener diode 50. The circuit is designed so that as the load current increases toward the 3 amperes, for which the power supply was designed, the increase in conduction of transistor 43 and the resulting reduction in Zener current of Zener diode 50 causing the Zener diode to approach the knee of the operating curve. An abnormal further increase in the load current required causes a further increase in the conduction of transistor 43, which results in a larger emitter current from transistor 43 flowing through the resistor 54 and the current conduction of the Zener diode 50 is reduced to a point below the kneeof the Zener curve, as shown in Figure 2, point 0, so that the voltage across the Zener diode no longer acts as a reference potential but drops extremely rapidly. This sudden drop in the potential across the Zener diode reduces the bias to transistor 43 and causes the transistor 43 to be cut off, thereby cutting oil the transistors 34 and 21. The transistor 21 is continued to be biased in the off condition as long as the output terminals continue shorted.

It will be noted that the base electrodeb of the tetrode transistor 21 is shorted to the emitter electrode 20 by the conductor 14 and thereby is also conductively connected to source terminal 11. This connection provides a low impedance between the base electrode and the emitter electrode of the tetrode transistor, so that the base-collector leakage current of the transistor is provided through the base electrode b In this manner the minimum collector current of tetrode 21 is limited to near the fundamental collector leakage current, often denoted as IcO, and does not include the amplified leakage current component. Under high temperature operating conditions it may be desirable to provide a reverse bias between the emitter 20 and the base electrode b in place of the direct connection. This may be accomplished, for example, by an auxiliary battery between the emitter and base electrode or by the use of a junction diode in series with the emitter electrode. The tetrode transistor provides decoupling between the signal applied to base b and the low impedance path connected to base b This is easily understood when it is realized that the resistance through the base wafer from base b to base b is in the order of 70 ohms whilethe impedance from emitter 20 to base b is approximately 4 ohms as is the impedance from emitter to base b This decoupling provided in the tetrode maintains the signal path to the tetrode isolated from the bias path so that there is no degeneration of the signal due to the bias path. Thus during conditions when the output is shorted and the regulator has switched into its fail-safe condition, substantially the entire power source potential appears across the tetrode transistor 21 and the current flowing therethrough is limited to the collector leakage current which may be in the order of a few milliamperes.

In general, while I have shown a specific embodiment of my invention, it is to :be understood that this is for the purpose of illustration and that my invention is to be limited solely by the scope of the appended claims.

I claim:

1. Semiconductor voltage regulator apparatus having fail-safe operation in the event of overload comprising: tetrode semiconductor means having a plurality of electrodes including a collector electrode, an emitter electrode, and first and second base electrodes; first and second regulator output terminals; first and second regulator power input terminals, said first and second power input terminals vbeing connected to a source of potential; means connecting said first power input terminal to said emitter electrode; means directly connecting said. second base electrode to said emitter electrode; connection means connecting said collector electrode to said first output terminal; compensating resistance means forming a POP.

tion of said connection means; potential divider resistance means connected from said collector electrode to said second input terminal, said potential divider means having an adjustable intermediate tap; means comprising a Zener diode and a resistance in series, connected between said first output terminal and said second input terminal, one terminal of said Zener diode being connected to said first output terminal; further semiconductor amplifier means, said means having a plurality of electrodes including a collector, an emitter and a base electrode, said emitter electrode being connected to the other terminal of said Zener diode, said base electrode being connected to said adjustable intermediate tap of said potential divider means; and conductive means connecting the collector electrode of said further semiconductor means to the first base electrode of said tetrode semiconductor means; said regulator means having a first normal condition of operation during which an increase in load current causes an increase in the bias to and an increase in the conduction of said further semiconductor means, and having an overload condition during which the bias is reversed to maintain said further semiconductor means cutoff.

2. Semiconductor voltage regulator appartus having fail-safe operation in the event of overload comprising: tetrode transistor means having a plurality of electrodes including a collector electrode, an emitter electrode, and first and second base electrodes; first and second regulator output terminals; first and second regulator power input terminals, said first and second power input terminals being connected to a source of potential; means connecting said first power input terminal to said emitter electrode; means directly connecting said second base electrode to said emitter electrode; connection means connecting said collector electrode to said first output terminal, compensating resistance means forming a portion of said connection means; potential divider resistance means connected from said collector electrode to said second input terminal, said potential divider means having an adjustable intermediate tap; means comprising a Zener diode and a resistance in series, connected between said first output terminal and said second input terminal, one terminal of said Zener diode being connected to said first output terminal; further transistor amplifier means, said means having a plurality of electrodes including a collector, an emitter and a base electrode, said emitter electrode being connected to the other terminal of said Zener diode, said base electrode being connected to said adjustable intermediate tap of said potential divider means; and conductive means connecting the collector electrode of said further transistor means to the first base electrode of said tetrode transistor means in current controlling relation thereto; said regulator means having a first normal condition of operation during which an increase in load current causes an increase in the bias to and an increase in the conduction of said further transistor means and having an overload condition during which the bias is reversed to maintain said further transistor means and said tetrode transistor means cutofi'.

3. Semiconductor voltage regulator apparatus having fail-safe operation in the event of overload, comprising: tetrode semiconductor control means having a semiconductive body and having a plurality of electrodes including an output electrode, an input electrode, and first and second control electrodes, said input and output electrodes making junction contact with said semiconductive body; first and second regulator output terminals; first and second regulator power input terminals, said first and second power input terminals being connected to a source of unregulated electrical potential; means directly connecting said first power input terminal to said input electrode;- means directly connecting said second control electrode to said input electrode to provide a low impedance path for the output electrode junction leakage current, whichpath bypasses said input electrode junction; connection means connecting said output electrode to said first output terminal, compensating resistance means forming an interm'ediate portion of said connection means; first resistance means connected from said output electrode to said second input terminal, said first resistance means having an adjustable intermediate tap; means, comprising a Zener diode and asecond resistance in series, connected between said first output terminal and said second input terminal, one terminal of said Zener diode being connected to said first output terminal; further semiconductor amplifier means, said means having a plurality of electrodes i11- cluding a collector, an emitter and a base electrode, said emitter electrode being connected to the other terminal of said Zener diode, said base electrode being connected to said adjustable intermediate tap of said first resistance means; and conductive means connecting the collector electrode of said further semiconductor means to the first control electrode of said tetrode semiconductor means; said regulator means having a first normal condition of operation during which an increase in load current causes an increase in the bias to an increase in the conduction of said further semiconductor means and said tetrode semiconductor means, and having an overload condition during which the bias potential applied to said further semiconductor means is reversed to maintain said further semiconductor means and said tetrode semiconductor means cutoff, the connecting means directly connecting said second control electrode to said input electrode being effective during the overload condition of operation to reduce the output current flowing in said output electrode to the fundamental leakage current of said output electrode junction.

4. Semiconductor voltage regulator apparatus having fail-safe operation in the event of abnormal overload comprising: tetrode semiconductor amplifier means having a plurality of electrodes including an output electrode, an input electrode, and first and second control electrodes; first and second regulator output terminals; first and second regulator power input terminals; a point of fixed potential; said first power input terminal being connected to a source of electrical energy, said second power input terminal and said second regulator output terminal being connected to said point of fixed potential; means connecting said first power input terminal to said input electrode; conductive coupling means connecting said second control electrode to said input electrode; conductive connection means connecting said output electrode to said first output terminal; first resistive means connected from said output electrode to said fixed potential point, said first resistive means having an adjustable intermediate tap; means comprising a Zener diode and a resistance in series, connected between said first output terminal and said fixed potential point, one terminal of said Zener diode being connected to said first output terminal; further semiconductor amplifying means, said means having a plurality of electrodes including at least a pair of input electrodes and an output electrode, the first of said input electrodes being connected to the other terminal of said Zener diode, the other of said input electrodes being connected to said adjustable intermediate tap; means connecting the output electrode of said further semiconductor means in current controlling relation to the first control electrode of said tetrode semiconductor means; compensating resistance means included in said conductive connection means for providing a potential thereacross the magnitude of which is proportional to the load current, said potential being effective to additionally increase the conductivity of said further semiconductor means with an increase in load current; said regulator means having a first normal condition of operation during which an increase in load current causes an increase in the bias to and an increase in the conduction of said further semiconductor means, and having an overload shutdown condition upon the output terminals becoming shorted during which the bias is reversed to maintain said semi conductor means cut off. 1 5. Semiconductor voltage regulator apparatus having fail-safe operation in the event of abnormal overload comprising: tetrode semiconductor amplifier means having a plurality of electrodes including an output electrode, an input electrode, and first and second control elecgtrodes; first and second regulator output terminals; first and second regulator power input terminals; said first power input terminal being connected to a source of potential, said second power input terminal and said second regulator output terminal being connected to a point of fixed potential; means connecting said first power input terminal to said tetrode semiconductor input electrode; conductive coupling means connecting said second control electrode to said first input terminal; conductive connection means connecting said output electrode to, said first output terminal; first resistive means connected. from said output electrode to said fixed potential point, said first resistive means having an adjustable intermediate tap; a Zener diode having one terminal thereof connected to said first output terminal; second resistive means connecting the other Zener diode terminal to said fixed potential point, said second resistive means being of a magnitude to limit the maximum current flowing in said Zener diode to a value which only slightly exceeds the knee of the Zener voltage curve of said Zener diode; further semiconductor amplifying means, said means having aplurality of electrodes including at least an input electrode, an output electrode and a common electrode, said common electrode being connected to the other terminal of said Zener diode, said input electrode being connected to said adjustable intermediate tap, said further semiconductor means being controlled by the potential diflerence between said input and common electrodes, the current flowing in such common electrode being efiective to reduce the current flowing in said Zener diode; means connecting the output electrode of said further semiconductor means in current controlling relation to the first control electrode of said tetrode semiconductor means; compensating resistance means included in said conductive connection means for providing a potential thereacross the magnitude of which is proportional to the load current, said potential being effective to additionally increase the conductivity of said further semiconductor means as a function of an increase in load current to said regulator output terminals; said regulator means having a first normal condition of operation during which an increase in load current causes an increase in the bias to and an increase in the conduction of said further semiconductor means, and having a load current overload operating condition during which the current flowing in the Zener diode is reduced to a point below the knee of the Zener voltage curve such that the bias is reversed to maintain said semiconductor means cut off.

6. Semiconductor regulated power supply apparatus having automatic fail-safe shut down in the event of overload, comprising: a source of potential to be regulated having first and second terminals; electrical load means which may vary in impedance, having first and second terminals; tetrode transistor means having a plurality of electrodes including a collector electrode, an emitter electrode, and first and second control electrodes; first connection means connecting one of said emitter and collector electrodes to the first terminal of said source; second connection means connecting the other of said emitter and collector electrodes to the first terminal of said load means, said second connection means comprising a conductive path having a resistive element intermediate its ends; first resistive means having end terminals and an intermediate connection, said first resistive means having its end terminals connected between the other of said emitter and collector electrodes and said second terminal of said source; Zener diode means; second resistive means; means connectingsaid Zener-diode means and said second resistive means in series between the first terminal of said load means and the second terminal of said source, one terminal of said Zener diode means being connected to said first terminal of said load means; said first resistive means, said Zener diode means and said second resistive means being connected across said regulated voltage output to sense the magnitude of the output voltage; second transistor means having a plurality of electrodes including at least a pair of input electrodes and an output electrode; means connecting one of said input electrodes to said intermediate connection and the other of said input electrodes to the junction of said Zener diode means and said second resistive means, whereby the conductivity of said second transistor means is controlled as a function of the output potential; further conductive means connecting said output electrode of said second transistor means to said first control electrode of said first transistor means in current controlling relation thereto; and means directly connecting the second base electrode to the emitter electrode of said first transistor means to provide a low impedance path for the collector junction leakage current, which path bypasses the emitter junction, said regulated power supply apparatus having a first normal condition of operation during which an increase in load current causes an increase in bias potential to said second transistor means whereby the conductivity of said first transistor is increased, and having an overload condition of operation wherein the bias potential to said second transistor means is reversed to render said first transistor means substantially non-conductive, the connection from the emitter to the second control electrode of said first transistor means being eifective during the period the overload condition remains to limit the collector current to the fundamental junction leakage current.

7. Semiconductor regulated power supply apparatus having automatic fail-safe shut down in the event of overload, comprising: a source of potential to be regulated having first and second terminals; electrical load means, which may require widely varying load currents having first and second terminals; tetrode transistor means having a plurality of electrodes including an input electrode, an output electrode, and first and second control electrodes; first connection means connecting one of said input electrodes to the first terminal of said source; second connection means connecting said output electrode to the first terminal of said load means; means connecting together said second source terminal and said second load means terminal, first resistive means having end terminals and an intermediate tap, said first resistive means having one terminal connected to said output electrode and the other terminal connected to said second terminal of said source; Zener diode means; second resistive means; means connecting said Zener diode means and said second resistive means in series between the first terminal of said load means and the second terminal of said load means, one terminal of said Zener diode means being connected to said first terminal of said load means, said first resistive means, said Zener diode means and said second resistive means being connected across said regulated voltage output to sense the magnitude of the output voltage and to provide a signal potential therefrom, the magnitude of which is a function of the load current; electronic current controlling means connected in current controlling relation to said first control electrode of said tetrode transistor means; means connecting said signal potential from said intermediate connection and the junction of said Zener diode means and said second resistive means in controlling relation to said electronic current controllinz means whereby the conductivity of said tetrode transistor means is controlled as a function of the output potential; and means directly connecting the second control electrode to the emitter electrode of said tetrode transistor means to provide a low impedance path for the collector leakage current, which path bypasses the emitter junction; whereby said regulated power supply apparatus has a first normal condition of operation during which an increase in load current causes an increase in bias potential to said electronic current controlling means whereby the conductivity of said tetrode transistor means is increased, and having an overload condition of operation wherein the bias potential to said electronic current controlling means is reversed to render said tetrode transistor means substantially nonconductive, the connection from the emitter to the second control electrode of said tetrode transistor means being effective during the period the overload condition remains to limit the collector current to the fundamental junction leakage current.

8. Semiconductor regulated power supply apparatus having automatic fail-safe shut down in the event of overload, comprising: variable load means having first and second terminals, said second terminal being connected to a fixed potential point, tetrode transistor means having a plurality of electrodes including an output electrode, an input electrode, and first and second control electrodes; first connection means connecting said input electrode to a potential source; load current compensating resistive means connecting the output electrode to the first terminal of said variable load means; first resistive means having an intermediate connection, said first resistive means being connected between the output electrode and said fixed potential point; Zaner diode means; second resistive means; means connecting said Zener diode means and said second resistive means in series between the first terminal of said lead means and said fixed potential point, one terminal of said Zener diode means being connected to said first terminal of said load means; said first resistive means, said Zener diode means and said second resistive means being connected across said regulated voltage output to sense the magnitude of the output voltage and provide therefrom a signal potential the magnitude of which is a function of the output current to said load means; electronic current controlling means connected to the first control electrode of said tetrode transistor means in current controlling relation thereto; means connecting said signal potential in controlling relation to said electronic current controlling means; and means directly connecting the second control electrode to the input electrode of said tetrode transistor means to provide a low impedance path for the output junction leakage current, which path bypasses the input junction; said regulated power supply apparatus having a first normal condition of operation during which an increase in load current causes an increase in bias potential to said electronic current controlling means whereby the conductivity of said tetrode transistor means is increased, and having an overload shutdown condition of operation wherein the bias potential to said second transistor means is reversed to render said tetrode transistor means substantially nonconductive, the connection from the input electrode to the second control electrode of said tetrode transistor means being efiective to limit the output current to the fundamental output junction leakage current during the period the overload condition remains.

No references cited. 

